Schools face a funding shortfall of £5.4 billion despite extra funding to cover teacher pay rises, six unions have warned.

The School Cuts coalition, which includes leadership unions NAHT and ASCL, the National Education Union and support staff bodies the GMB, Unison and Unite, has published its latest analysis based on government figures for school funding between 2015-16 and 2018-19.

Schools are in the invidious position of having to decide on the least-worst option of where to make cuts or they will become insolvent

The analysis factors in extra funding allocated by the government to schools this year to cover teacher pay rises authorised by ministers last year, and for the first time also includes pupil premium and 16 to 19 education funding allocations.

The unions compared funding allocated for all of these elements in 2018-19 with the amount allocated three years ago, adjusted for inflation and other cost increases.

“School budgets are at absolute breaking point,” warned NAHT general secretary Paul Whiteman. “School leaders have made all the obvious savings. Now, class sizes are rising and the range of subjects schools can offer is shrinking as they desperately try to balance the books.”

ASCL’s general secretary Geoff Barton added: “Schools across the country have had to make severe cuts and there are more on the way as reserves are drained and deficits increase.

“The reality of budget cuts is that schools have to operate with reduced staffing and this impacts on educational provision, such as less additional support for children and fewer curriculum choices. Schools are in the invidious position of having to decide on the least-worst option of where to make cuts or they will become insolvent.”

The latest analysis is likely to cause a headache for the government in the wake of high-profile interventions from Conservative MPs over school funding.

The move by School Cuts to update their analysis comes after its statisticians were criticised by the UK Statistics Authority, and after the unions were forced to correct a significant blunder in their figures last year.

In January, the UKSA rebuked School Cuts for using “misleading statistics”. The watchdog took particular issue with the unions’ claim that 91 per cent of schools face funding cuts. The unions said they stood by the claim, and have reissued it today.

And last June, the coalition was forced to admit it had incorrectly claimed that schools would see a real-terms drop in per-pupil funding in 2018-19, after it emerged that £450 million of central school services block funding had not been factored in to its calculations.

The DfE said the School Cuts analysis was “misleading”, but didn’t expand on why. A spokesperson added: “The Secretary of State has made clear that as we approach the next spending review, he will back head teachers to have the resources they need to deliver a world class education.”

However, the School Cuts coalition, which runs a website allowing schools to calculate the impact of funding cuts on their own budgets, isn’t the only organisation to have been criticised over its use of funding statistics.

Last October, UKSA chief Sir David Norgrove wrote to the education secretary Damian Hinds, DfE permanent secretary Jonathan Slater and chief statistician Neil McIvor with “significant concerns” about the department’s use of stats.

The watchdog criticised a tweet and blog by the DfE about education funding, claiming figures were “presented in such a way as to misrepresent
changes in school funding”.

In the tweet, school spending figures “were exaggerated by using a truncated axis, and by not adjusting for per pupil spend”. In the blog, an international comparison of spend which “included a wide range of education expenditure unrelated to publicly funded schools” was used, rather than a comparison of school spending alone.

A DfE spokesperson said: “We believe these figures are misleading. While we recognise that schools have faced budgeting challenges, this government has prioritised school funding, while taking difficult decisions in other areas of public spending – protecting the schools budget overall for 5 to 16 year olds in real terms since 2010.

“School funding in England is at its highest ever level and since 2017 we have given every local authority in England more money for every pupil in every school.”